Human aging is accompanied by both physical and behavioral evidence of a decline in the functioning of a brain structure known as the hippocampus. The hippocampus is selectively vulnerable to a number of degenerative changes which appear to be strongly related to a marked decline of recent memory in old age. The latter is the major human symptom of hippocampal system damage. Rats might also have a similar decline in hippocampal in old age since 1) The RNA content of hippocampal neurons declines in old age and 2) at least a few observations suggest behavior indicative of hippocampal hypofunction in old rats. This study will involve the administration of test batteries to people and rats of various ages. The tests measure hippocampal functioning, either in fact or in theory. One major purpose of this study is to discover whether parallels will exist in age-related changes in rats and in people. A major goal is the establishment of an animal model of human aging, the implications of which are obvious. Rodents can then be employed in the study of the causes and (hopefully) cures of adverse changes in old age. Another goal of this research is the use of people with memory defects in an analysis of memory itself. Many exciting preliminary observations about memory have already been made and will be followed up. Finally, through the use of a test battery it will be possible to evaluate the degree to which age-related changes reflect a decline in a single underlying variable. The performance of people on the various tests at various ages will allow an evaluation of several different theories and ideas about aging and about brain functioning.